Heterochromia
Although Yuna seems Asian, we can notice that her eyes are from different colors like the famous actress Jane Seymour or singer David Bowie. She's heterochromic. In French, we call that vairon. It comes from the Latin varius which means various. In medical terms, this particularity is called heterochromia. Heterochromia is a term used to describe variations in the color of the iris, the colored portion of the eye. Vision is completely normal for these individuals and it's not considered a medical problem but rather a normal variation in eye color. I think that's pretty and original.

The reason why Yuna is heterochromic in the game is because she's half Al Bhed by her mother (her father married Cid's sister). Since all Al Bhed have green eyes (cf. Rikku, Cid, Brother etc.), it's not wrong to say that being mixed, Yuna shows her heritage physically by her eyes: one green, after her mother, and one blue, like her father's — High Summoner Braska.

Resemblances
All "Final Fantasy" heroines seem to look alike since the saga went on a realistic style: Tifa and Aerith from "Final Fantasy VII: Advent Children", Rinoa from "Final Fantasy VIII" and Garnet from "Final Fantasy IX". Since this is the one and same character designer, Tetsuya Nomura (except for Garnet), and motion actress, Mayuko Aoki, behind the digital life of those natural beauties, no wonder you get this déjà vu feeling. For the fun of it, I found five other fictional and real females bearing an uncanny resemblance to Yuna. Look!

Yuna looks a lot like Nozomi from the game Shenmue. They could be sisters! Nozomi may be the closest game girl ever created who resembles to Yuna. The only small differences are the face features and the haircolor.

Moemi is a character from the manga "Video Girl Ai" by M.Katsura. I thought that she resembled Yuna both by her personality and her appearance. They are the pretty and gentle kind yet have a great inner strength of personality.

Actress Jennifer Aniston is the first real woman I've thought of if I had to pick a real life Yuna, although Jennifer's face is more angular. You can't deny the opposite picture quite speaks for itself.

The story behind this picture is actually interesting. That game girl named Sakoto was actually mistaken for Yuna in a wallpaper site. Upon digging info, I found out she came from an erotic video game called "Requiem Hurts".

Actress Shannen Doherty's resemblance to Yuna hasn't come to me at first, because she's grown too old to look like her today — but her rounded face, short hairstyle and green eyes of a time made me think of our heroine.